Summary

On 4 November 2007, a Boeing Company 777-2D7 (777) aircraft,
registered HS-TJW, was being operated on a scheduled passenger
service from Bangkok, Thailand to Melbourne, Vic. with 17 crew and
277 passengers on board. During the conduct of a non-directional
beacon (NDB) non-precision approach to runway 16 at Melbourne, the
crew descended the aircraft below a segment minimum safe altitude.
Soon after, the crew received two enhanced ground proximity warning
system cautions. At that time, the crew became visual with the
ground below and the Melbourne aerodrome controller observed the
aircraft 'unusually low for an aircraft'. The crew levelled the
aircraft and made a visual approach and landed, on runway 16.

The investigation found that the aircraft had descended below a
critical altitude whilst carrying out an NDB approach and that the
crew did not monitor the aircraft's progress correctly during the
NDB approach.

The aircraft operator had known about the difficulties in flying
approaches without constant angle approach paths and was in the
process of training flight crews on procedures specific to NDB
approaches when the incident occurred. In October 2007, the
operator introduced a training program to instruct pilots on a new
method to conduct those approaches. At the time of the incident,
the pilots of the 777 had not undergone that training.

Preliminary

On 4 November 2007, a Boeing Company 777-2D7 aircraft,
registered HS-TJW, was being operated on a scheduled passenger
service from Bangkok, Thailand, to Melbourne, Vic, with 17 crew and
277 passengers on board. During a non-directional beacon (NDB)
non-precision approach to runway 16 at Melbourne Airport, the
aircraft descended below the segment minimum safe altitude at 6.8
distance measuring equipment (DME, a measure in nautical miles).
Soon after, the crew received two enhanced ground proximity warning
system (EGPWS) cautions. The crew then levelled the aircraft and
conducted a visual approach and landing on runway 16.